Provided is a therapeutic method exclusively targeting an amyloid .beta. protein (A.beta.) having a specific turn structure of A.beta.. Specifically provided is an antibody which specifically recognizes an amyloid .beta. having a turn structure at amino acids positions 22 and 23. Also provided are a medicinal composition comprising, as the active ingredient, an antibody specifically recognizing a toxic conformer of amyloid .beta., an assay kit for a toxic conformer of amyloid .beta., a diagnostic for Alzheimer's disease, etc.

Claim:

The invention claimed is:

1. An isolated antibody or an immunoreactive fragment thereof comprising the CDR1, CDR2 and CDR3 of the H-chain and the CDR1, CDR2 and CDR3 of the L-chain of theantibody produced by the hybridoma deposited as registration No. FERM-11290.

2. The antibody or fragment of claim 1 wherein one or more amino acids are substituted, deleted, modified, added and/or inserted and retains the antigen-binding specificity of the antibody produced by the hybridoma deposited as registration No.FERM-11290.

3. The antibody of or fragment claim 1 wherein the antibody or fragment is identical to that produced by hybridoma deposited as registration No. FERM-11290.

4. A kit for measuring amyloid .beta. having a turn structure at amino acid positions 22 and 23, comprising an antibody or fragment of claim 1 and reagents for detecting binding of said antibody to said amyloid .beta..

5. The antibody or fragment of claim 1 that has VH and VL of the antibody produced by the hybridoma deposited as registration No. FERM-11290.

6. The antibody or fragment of claim 5 which further comprises the constant regions of a human antibody.

7. A pharmaceutical composition comprising an antibody of claim 1 as an active ingredient.

8. A method to treat Alzheimer's disease which comprises administering to a subject in need of said treatment an effective amount of the pharmaceutical composition of claim 7.

9. A method for measuring the level of amyloid .beta. having a turn structure at amino acid positions 22 and 23 in a sample, comprising contacting the sample with an antibody or fragment of claim 1, and measuring any complex formed with saidantibody or fragment.

10. A method for providing information for diagnosis of Alzheimer's disease in a test subject comprising steps of: contacting a sample derived from the test subject with at least one antibody or fragment of claim 1, and measuring binding of theantibody or fragment to any amyloid 0 having a turn structure at amino acid positions 22 and 23, determining a level of amyloid .beta. having a turn structure at amino acid positions 22 and 23, whereby the level of amyloid .beta. having a turnstructure at amino acid positions 22 and 23 determines presence or absence or severity of Alzheimer's disease in the subject.

11. A method for measuring a ratio of amyloid .beta. having a turn structure at amino acid positions 22 and 23 relative to total amyloid .beta. in a sample, comprising: measuring a level of total amyloid .beta. in the sample, contacting thesample with at least one antibody or fragment of claim 1 and measuring any level of amyloid .beta. having a turn structure at amino acid positions 22 and 23, and calculating the ratio of the measured level of amyloid .beta. having a turn structure atamino acid positions 22 and 23 to the measured level of total amyloid .beta..

12. A method for providing information for diagnosis of Alzheimer's disease in a subject, comprising: measuring a level of total amyloid .beta. in a sample derived from the test subject, contacting the sample with at least one antibody orfragment of claim 1 and measuring a level of amyloid .beta. having a turn structure at amino acid positions 22 and 23, calculating the ratio of the measured level of amyloid .beta. having a turn structure at amino acid positions 22 and 23 relative tothe measured level of total amyloid .beta., whereby the ratio of the measured level of amyloid .beta. having a turn structure at amino acid positions 22 and 23 relative to the measured level of total amyloid .beta. determines presence or absence orseverity of Alzheimer's disease in the subject.